On linguisitc puritanism and adherence to the standard

There are essentially two ways of looking at grammar. There is the prescriptive approach which tells people which forms of language to use based on the standard and the descriptive approach which explains naturally occurring grammatical phenomena. For this blog I will be looking at the prescriptivist approach to language grammar.
My title for this blog may seem a bit esoteric, but this is a phenomenon that almost everyone is familiar with. Indeed, I'm sure that your grade school teachers did their part to teach you what is standard and what is non-standard English Many people are very sensitive, and many are not so sensitive, to the correct and incorrect ways of speaking English. This is less of a case of right and wrong, and should more accurately be labeled as standard and non-standard distinction. Standard being the form of English which we deem "right" or "correct". These linguistic puritans make sure that speakers of the English language, or at least they themselves, are using English the proper way. It should come as no surprise to us then, that a large number of the population are like this, me included, because of the correction we have received through our lives from teachers, parents, etc.
Linguistic puritanism is an interesting movement. It is good because it means that since we are all at least familiar with standard English we can understand almost all other speakers of English with no difficulty. The problematic part, however, is what it seeks to accomplish. A whole-hearted linguistic puritan would desire strict adherence to the standard wherein there may be no room for linguistic change at all. This is a problem because languages are either changing or dead. This sort of extremism is not encountered much, however, so English dying any time soon is of little concern.
When we begin to think of English forms as standard and non-standard we also encounter another little interesting tidbit. Should we be so concerned with what is "right" English if the changes are just necessary and logical changes in the progression of English? Why do differences in English seem to offend us on a moral level where we can classify "good" forms of English and "bad" form? For instance I know many people who are offended or somewhat annoyed at least by the wide sweeping use of "seen" as the past tense of "saw" as in "I seen it". There should be nothing "wrong" about this use of 'seen' as it is a simple matter of dialectal variation and standard English not some moral code that we must adhere to. There is nothing "more correct" about the standard form of English or the rules laid down in grammar textbooks. (It is also interesting to note that some of those rules were simply made up by the grammarians themselves.)
So if you have made it this far, pause for a minute to look at your own approach to language grammar. Do you take the puritan approach and side with the prescritivist or do you tend to not worry about maintaining "pure" English with the descriptivist?
Are you somewhat morally offended when people use forms of English improperly, and do you have any insights as to why this may occur?